1. Field of the Invention
This invention relates to an image information read-out apparatus, and more particularly to an image information read-out apparatus in which reading light is projected in a line onto an image-bearing medium bearing thereon an image and image-bearing light bearing thereon the image on the image-bearing medium and emitted from the recording medium upon exposure to the reading light is read out by a line sensor.
2. Description of the Related Art
When certain kinds of phosphor are exposed to a radiation, they store a part of energy of the radiation. Then when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light or a laser beam, light is emitted from the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is generally referred to as xe2x80x9ca stimulable phosphorxe2x80x9d. In this specification, the light emitted from the stimulable phosphor upon stimulation thereof will be referred to as xe2x80x9cstimulated emissionxe2x80x9d. There has been put into wide use as a computed radiography a radiation image recording and reproducing system using a stimulable phosphor sheet (a sheet provided with a layer of the stimulable phosphor).
In the radiation image recording and reproducing system, a stimulable phosphor sheet is exposed to a radiation passing through an object such as a human body to have a radiation image information of the object stored on the stimulable phosphor sheet, a stimulating light beam such as a laser beam is caused to two-dimensionally scan the stimulable phosphor sheet, thereby causing each part of the stimulable phosphor sheet exposed to the stimulating light beam to emit the stimulated emission, the stimulated emission is photoelectrically detected, thereby obtaining an image signal (a radiation image signal) representing the radiation image information, the radiation image signal thus obtained is subjected to image processing such as gradation processing and/or frequency processing and a radiation image of the object is reproduced as a visible image for diagnosis on the basis of the processed radiation image signal on a recording medium such as a photographic film or a display such as a CRT.
In the radiation image information read-out apparatus employed in the radiation image recording and reproducing apparatus, it has been proposed to use a line light source which projects a line beam onto the stimulable phosphor sheet as a stimulating light source and to use a line sensor having an array of photoelectric convertor elements extending in the main scanning direction (the longitudinal direction of the line beam) as a means for photoelectrically reading out the stimulated emission. The line beam and the line sensor are moved relative to the stimulable phosphor sheet in the sub-scanning direction (the direction perpendicular to the longitudinal direction of the line beam) by a scanning means. By the use of a line beam and a line sensor, the reading time is shortened, the overall size of the apparatus can be reduced and the cost can be reduced. See, for instance, Japanese Unexamined Patent Publication Nos. 60 (1985)-111568, 60 (1985)-236354, and 1 (1989)-101540. In such a radiation image information read-out apparatus, the line sensor is positioned close to the stimulable phosphor sheet and an erecting unit optical system is provided between the line sensor and the stimulable phosphor sheet in order to collect the stimulated emission on the light receiving face of the line sensor.
Also when the stimulating light source is a point scan type light projecting means which causes a light beam to scan the stimulable phosphor sheet, a line sensor is sometimes employed as the photoelectric read-out means.
The length of the line sensor should be equivalent to the width of the stimulable phosphor sheet which is generally 35 cm to 43 cm. Since the sensor chips commercially available at present is from several tens mm to about 100 mm in length, a line sensor formed by arranging a plurality of sensor chips in a row has been employed in the radiation image information read-out apparatus. Since each of the sensor chips is packaged, the parts between adjacent sensor chips form dead zones (noneffective zones) where the stimulated emission cannot be detected. Accordingly, stimulated emission which impinges upon the noneffective zones of the line sensor cannot be detected, which generates artifact in images obtained.
This problem may be overcome by arranging a plurality of combinations of a line sensor (having noneffective zones) and an erecting unit optical system in parallel to the longitudinal direction of the line beam. However this approach is disadvantageous in that one or more additional erecting unit optical system is required, which adds to the cost, and even with such a structure, the noneffective zones of the respective line sensors make it difficult to uniform the light receiving condition over the entire length of the line beam.
In the field of biochemistry and the molecular biology, there has been known a fluorescence detecting system in which detection of the gene sequence, the gene expression level, and the pathway and/or condition of metabolism, absorption and excretion of material administered to a mouse; and separation, identification, and evaluation of molecular weight and properties of protein can be carried out by reading out image information on a sample in which a specific organism-derived material labeled with fluorescent pigment is distributed. In the fluorescence detecting system, for example, a gel support on which a specific DNA fraction (an organism-derived material) labeled with fluorescent pigment is distributed is obtained, exciting light which excites the fluorescent pigment is projected onto the gel support, fluorescence emitted from the gel support is photoelectrically read, thereby obtaining image information representing the distribution of the DNA fraction labeled with the fluorescent pigment, and the distribution of the DNA fraction is displayed on, for instance, a CRT display on the basis of the image information thus obtained.
Also in this fluorescence detecting system, there has been proposed an arrangement which comprises a stimulating (exciting) light source, a line sensor and a sub-scanning means similar to those employed in the aforesaid radiation image information read-out apparatus. Also in the fluorescence detecting system of this arrangement, there are involved problems described above in conjunction with the radiation image information read-out apparatus.
In view of the foregoing observations and description, the primary object of the present invention is to provide an image information read-out apparatus which employs a line sensor formed of a plurality of sensor chips and can nevertheless read an image free from artifact due to the noneffective zones between sensor chips.
In accordance with the present invention, there is provided an image read-out apparatus comprising a reading light projecting means which projects reading light in a line-like pattern extending in a main scanning direction onto an image-bearing medium bearing thereon image information, an image-bearing light detecting means having a line sensor which extends along the line-like portion of the image-bearing medium exposed to the reading light to receive image-bearing light emitted from the portion exposed to the reading light and converts the amount of image-bearing light to an electric signal, and a sub-scanning means which moves one of the image-bearing light detecting means and the image-bearing medium relatively to each other in a sub-scanning direction intersecting the main scanning direction, wherein the improvement comprises that
the image-bearing light detecting means further comprises an erecting unit optical system which is disposed along the portion of the image-bearing medium exposed to the reading and focuses the image-bearing light on the line sensor and an optical element array formed by a plurality of first and second optical elements which are alternately arranged along the erecting unit optical system and lead the image-bearing light passing through the erecting unit optical system in different directions, and
said line sensor comprises a first sensor which receives light led by the first optical elements and a second sensor which receives light led by the second optical elements.
The image-bearing light is light which is emitted from the portion of the image-bearing medium exposed to the reading light and bears thereon a part of the image born by the portion of the image-bearing medium. The image-bearing light emitted from the portion of the image-bearing medium exposed to the reading light may be any of light reflected at the portion, light passing through the portion and light generated by the portion so long as it bears the image born by the portion of the image-bearing medium exposed to the reading light.
The reading light projecting means may be either of a point scan type which causes a point light beam to scan the image-bearing medium in a line in the main scanning direction or of a line irradiation type which projects a line light beam extending in the main scanning direction onto the image-bearing medium. That is, the portion of the image-bearing medium exposed to the reading light is the portion scanned by the point light beam in the former case, and the portion exposed to the line light beam at one time in the latter case.
When the image-bearing medium is a stimulable phosphor sheet, the image-bearing light is the stimulated emission. That is, the image information read-out apparatus of this invention can be employed as a radiation image information read-out apparatus for said computed radiography.
It is preferred that the stimulable phosphor sheet be anisotropic and radiates the stimulated emission in a direction at a predetermined angle to the direction of thickness of the stimulable phosphor sheet. In this case, it is preferred that the image-bearing light (stimulated emission) detecting system be arranged so that the stimulated emission incident face of the erecting unit optical system is positioned in perpendicular to the direction at the predetermined angle to the direction of thickness of the stimulable phosphor sheet.
The image-bearing medium may be a medium bearing thereon a fluorescent material image. In this case, the image-bearing light is fluorescence. That is, in this case, the image read-out apparatus of the invention may be used as an image read-out apparatus for the aforesaid fluorescence detecting system.
The medium bearing thereon a fluorescent material image is, for instance, a gel support on which a specific DNA fraction (an organism-derived material) labeled with fluorescent pigment is distributed, and the expression xe2x80x9cbearing thereon a fluorescent material imagexe2x80x9d should be broadly interpreted to include both a case where the medium bears thereon an image of the sample labeled with fluorescent pigment and a case where enzyme is bonded with the labeled sample, the enzyme is brought into contact with a fluorescent substrate to change the substrate into a fluorescent material which emits fluorescence, and the medium bears an image of the fluorescent material thus obtained.
Combinations of fluorescent pigment which is used for forming a labeled sample image on a medium and a wavelength of the reading light (exciting or stimulating light) for causing the pigment to emit fluorescence are as follows. When the reading light is a laser beam of 470 nm or 480 nm, the fluorescent pigment may be any so long as it can be excited by a laser beam at the wavelength. For example, Fluorescein (C.I. No. 45350), Fluorescein-X represented by the following structural formula (1), YoYo-1 represented by the following structural formula (2), ToTO-1 represented by the following structural formula (3), Yo-Pro-1 represented by the following structural formula (4), Cy-3(copyright) represented by the following structural formula (5), Nile Red represented by the following structural formula (6), BCECF represented by the following structural formula (7), Rohdamine 6G (C. I. No. 45160), Acridine Orange (C.I. No. 46005), SYBR Green (C2H6OS), Quantum Red, R-Phycoerythrin, Red 613, Red 670, Fluor X, Fluorescein-labeled amidite, FAM, AttoPhos, Bodipy phosphatidylcholine, SNAFL, Calcium Green, Fura Red, Fluo 3, AllPro, NBD phosphoethanolamine, and the like may be preferably employed. When the reading light is a laser beam of 633 nm or 635 nm, the fluorescent pigment may be any so long as it can be excited by a laser beam at the wavelength. For example, Cy-5(copyright) represented by the following structural formula (8) and Allphycocyanin may be preferably employed. When the reading light is a laser beam of 530 nm or 540 nm, the fluorescent pigment may be any so long as it can be excited by a laser beam at the wavelength. For example, Cy-3(copyright) represented by the following structural formula (5), Rohdamine 6G (C. I. No. 45160), Rohdamine B (C.I. No. 45170), Ethidium Bromide represented by the following structural formula (9), Texas Red represented by the following structural formula (10), Propidium Iodide represented by the following structural formula (11), POP-3 represented by the following structural formula (12), Red 613, Red 670, Cardoxyrohdamine (R6G), R-Phycoerythrin, Quantum Red, JOE, HEX, Ethidium homodimer, Lissamine rhodamine B peptide and the like may be preferably employed.
Structural Formula (1)xcx9c(12) 
For example, the reading light projecting means may be a line irradiation type light beam projecting means comprising a combination of a slit and a fluorescent lamp or a cold cathode fluorescent lamp or a combination of an optical system such as a cylindrical lens and a light source such as an LED array, an LD array or a broad area laser as well as a point scan type light beam projecting means comprising a light source such as an LED and a light beam scanning optical system such as a polygonal mirror.
It is possible to provide a plurality of reading light projecting means which emit light of different wavelengths so that one of the reading light projecting means is selectively employed according to the kind of image-bearing medium to be used.
It is preferred that the length of the portion of the image-bearing medium exposed to the reading light in the main scanning direction be not smaller than the width of the image-bearing medium.
The erecting unit optical system may be, for instance, a refractive index profile type lens array such as a SELFOC(copyright) lens array or a rod lens array, which is formed by an imaging system where the object plane and the image plane are in one to one correspondence, a cylindrical lens, a biaxial lens, an aspheric lens array (see, Japanese Unexamined Patent Publication No. 6 (1994)-208081) a slit or fiber optics.
The reading light projecting means and the image-bearing light detecting means may be disposed either on the same side of the image-bearing medium sheet or on opposite sides of the sheet. However, in the latter case, the support sheet and the like of the image-bearing medium sheet should be permeable to the image-bearing light.
When each of the first and second sensors is provided with effective areas, where the sensor can detect light, and noneffective areas, where the sensor cannot detect light, which are alternately arranged in the main scanning direction, for example, the part of the image-bearing light led by the first optical elements is caused to impinge upon the effective areas of the first sensor and the part of the image-bearing light led by the second optical elements is caused to impinge upon the effective areas of the second sensor.
When each of the first and second sensors comprises a plurality of sensor chips, each comprising a plurality of photoelectric convertor elements linearly arranged in a row, arranged end to end, the central areas of the respective sensor chips where the photoelectric convertor elements exist are the effective areas and the end portions of the respective sensor chips where no photoelectric convertor element exists are the noneffective areas.
In the image information read-out apparatus of the present invention, it is preferred that the first and second sensors are disposed so that the effective areas of the first and second sensors overlap each other in the main scanning direction at portions corresponding to boundaries between the first and second optical elements of the optical element array and there is provided pixel signal adder means which adds up pixel by pixel outputs of the first and second sensors for each pixel in the portions corresponding to boundaries between the first and second optical elements of the optical element array. The boundary between the first and second optical elements of the optical element array as said here need not necessarily have only one pixel width in the main scanning but may have a multiple pixel width. That is, the boundary may be represented by a plurality of pixels near to pixels which form an exact boundary.
The optical element array may be formed by either first and second optical elements one of which transmits the image-bearing light and the other of which reflects the same, or first and second optical elements which reflect the image-bearing light in different directions.
It is preferred that the optical element array itself has a function of cutting the reading light. For example, this may be realized by forming the optical element array itself of a material which absorbs light at the wavelength of the reading light or by disposing an interference filter, which transmits the image-bearing light but does not transmit the reading light, in front of the light incident face of the optical element array.
When the first and second optical elements are arranged to reflect the image-bearing light in different directions, the optical element array may be given a function of cutting the reading light by forming the reflecting surfaces of the first and second optical elements by dichroic mirrors which reflect the image-bearing light but transmit the reading light.
A reading light cut filter which transmits the image-bearing light but does not transmit the reading light (e.g., a sharp cut filter or a bandpass filter) maybe provided between the image-bearing medium and the line sensor.
The image information read-out apparatus of the present invention may be provided with a plurality of sets of image-bearing light detecting means. In this case, it is preferred that the optical element arrays be arranged so that the boundaries between first and second optical elements are positioned in different positions, image-bearing light detecting means by image-bearing light detecting means as seen in the main scanning direction.
In the image information read-out apparatus of the present invention where the image-bearing light detecting means has an optical element array formed by a plurality of first and second optical elements which are alternately arranged and lead light in different directions, and first and second sensors which receive light led by the first and second optical elements, the image-bearing light emitted from the part of the image-bearing medium exposed to the reading light is uniformly detected by the line sensor over the entire width of the image-bearing medium.
Even if each sensor has effective areas and noneffective areas alternately arranged in the main scanning direction, when such an optical element array and a pair of sensors are employed, the image-bearing light emitted from portions corresponding to noneffective areas of one of the sensors can be detected by the effective areas of the other sensor, whereby the image-bearing light entering the erecting unit optical system can be uniformly detected over the entire width of the image-bearing medium, and at the same time, generation of artifact can be suppressed as compared with when only one set of stimulated emission detecting means is employed.
When the first and second sensors are disposed so that the effective areas of the first and second sensors overlap each other in the main scanning direction at portions corresponding to boundaries between the first and second optical elements of the optical element array and there is provided pixel signal adder means which adds up pixel by pixel outputs of the first and second sensors for each pixel in the portions corresponding to boundaries between the first and second optical elements of the optical element array, even if the image-bearing light from the portions of the image-bearing medium corresponding to the boundaries is detected partly by the first sensor and partly by the second sensor, the whole image-bearing light from the portions can be detected under substantially the same condition as other portions by adding the outputs of the first and second sensors, whereby discontinuity of the data at boundaries of the optical elements can be detected and a smooth image suppressed with artifact can be obtained.
When the optical element array itself has a function of cutting the reading light, the reading light can be prevented from impinging upon the line sensor without additionally providing a reading light cut filter.
Further when a plurality of sets of image-bearing light detecting means are provided, light collecting efficiency is enhanced and an image higher in S/N can be obtained, whereby, for instance, image diagnosis can be performed at a higher reliability.
Further, when a stimulable phosphor sheet which is anisotropic and radiates the stimulated emission in a direction at a predetermined angle to the direction of thickness of the stimulable phosphor sheet is employed as the image-bearing medium and the stimulated emission detecting means (the image-bearing light detecting means) is arranged so that the stimulated emission incident face of the erecting unit optical system is positioned in perpendicular to the direction at the predetermined angle to the direction of thickness of the stimulable phosphor sheet, the stimulated emission can be detected more efficiently and an image further higher in S/N can be obtained.